Rethinking Neuromyelitis Optica (Devic Disease)

Neuromyelitis optica (NMO), or Devic disease, has been distinguished from multiple sclerosis (MS) by the presence of optic neuritis that is usually bilateral, simultaneous, and often severe, myelopathic findings accompanied by longitudinally extensive spinal cord imaging abnormalities, no brain imaging abnormalities typical of MS, and often rapid progression to debility and even death. Researchers at the Mayo Clinic have identified an immunoglobulin marker of NMO (the "NMO antibody") that binds selectively to the aquaphorin-4 water channel and may play a causative role. This marker has been found in Japanese patients with opticospinal MS, prompting the suggestion that NMO and Japanese opticospinal MS are the same disorder. The NMO antibody, which predicts frequent relapse of myelopathy and optic neuritis, is also found in patients with lupus erythematosus and Sjögren syndrome who also have severe optic neuritis and longitudinally extensive myelitis. Because this antibody is also found in patients with optic neuritis and myelitis who have brain signal abnormalities atypical of MS, the diagnosis of NMO has been revised to allow inclusion of these brain imaging abnormalities. Proper distinction of NMO from MS is important because the two disorders may respond differently to immune modulatory therapy.